There is need in building optimal architectures to perform THz switching inside the small cavity. We want to minimize switching power, signal loss, response time while ensuring high on/off extinction ratio and low energy to control the switch.
Slow EM wave at THz speed supported by a highly conducting surface resembles surface plasmon polariton (SSP) modes and, henceforth, is called pseudo or spoof surface plasmon polariton (SSPP) modes.
The promising capability of SSPP modes is the miniaturization of THz elements and devices on a sub-wavelength scale, thus leading to the development of compact, ultrafast, and low power digital RF-THz circuits.
Design flexibility of metallic structures provides a promising way toward controlling or steering THz signal in future communication and digital circuits. Sub-wavelength metallic gap structures with a periodic array of grooves to increase slow down factor S=vc/vg, defined as the phase velocity over the group velocity, and use pass-band and stop-band characteristics similar to photonic crystals.
Basic architectures of the invention comprises a THz logic block by combining two double-sided corrugated waveguides with a sub-wavelength cavity, having one or more grooves with shorter height than the periodic waveguide grooves. This new THz structure is called the waveguide-cavity-waveguide (WCW) structure. Specifically, small cavity enables us to confine the EM wave for a long time in a very small volume. Therefore, the arbitrarily designed cavity with high quality factor (Q) and small effective volume (Veff) can be utilized for efficient switches.
The switching junction designed by high quality factor Q and small effective volume Veff enables us to obtain efficient THz switching functionality by achieving small refractive index modulation δn/n.
In addition, THz switching can also be obtained by using the loss induced modulation δα.